The Singer 301 motor has a sealed bearing in the top. It is not unusual for the bearing to lose its lubrication over time and then the bearing becomes noisy. If your Singer 301 squeals or runs loudly it is probably in need of a new top motor bearing.
This bearing is a perfect fit and will restore quiet running to your machine.
Also fits the motors on the 401, 403, 404, 500, and 503 Singers.